Unsteady Heartbeat Could Spell Early Dementia

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An irregular heartbeat may be a sign you're on the fast track to
dementia, according to a new study.

While thinking and memory problems are common in the elderly, the
study of more than 5,000 people over age 65 showed that those
with the
heart condition atrial fibrillation tend to suffer mental
decline earlier than people without the heart condition.

The reason for the link is unclear, and the findings don't mean
that everyone with atrial fibrillation will suffer earlier mental
decline, said study researcher Evan Thacker, a statistician in
the department of epidemiology at the University of Alabama at
Birmingham. "One person who has atrial fibrillation may not have
any memory
or thinking problems at all."

But as a group, people in the study with atrial fibrillation
reached the threshold where mental decline is considered to be
dementia two years earlier than those without the heart
condition, according to the study published today (June 5) in the
journal Neurology.

A few points missed means many troubles

In people with atrial fibrillation, misfiring electrical signals
cause an atypical heartbeat. The Centers for Disease Control and
Prevalence estimated 2.66 million people in the U.S. had atrial
fibrillation in 2010. But the CDC expects 12 million people will
have it by 2050.

Thacker's study used data from the large Cardiovascular Health
Study done in the 1990s. Participants had their heart health
measured, and took two types of mental tests each year over the
course of about seven years. The researchers excluded
participants who had had a stroke or a previous diagnosis of
atrial fibrillation, before the study's start.

One test, called the Modified Mini-Mental State Examination
(3MSE), measures global thinking abilities on a 100-point scale.
The 3MSE tests whether you know where you are and what day it is,
your language skills, or if you can copy interlocking shapes from
a piece of paper. The other test, called the Digit Symbol
Substitution Test (DSST), measures quick-thinking and
multitasking.

Researchers found that people who developed atrial fibrillation
during the study began doing worse on both mental tests. The
results showed that the average score of people ages 80 to 85
fell by 6.4 points on the 3MSE over the study period. But the
average score of people with atrial fibrillation declined 10.3
points.

And a 5- or 10-point drop on either test can indicate a
noticeable difference in everyday life. "They may notice
problems in memory that are more serious than remembering
where you put your keys," Thacker said.

"It could be not having a good enough memory to find your way
home after shopping," he said. In more serious cases it could
mean a person can't put together a meal, or manage finances.

Behind the heart-brain connection

The findings are important, said Dr. Allyson Zazulia, associate
professor of neurology at the Washington University School of
Medicine in St. Louis, because "both atrial fibrillation and
dementia are, of course, huge problems in the elderly."

Thacker's study couldn't explain how atrial fibrillation might be
related to memory problems. And at present, doctors don't even
know if treating atrial fibrillation would help or hurt a
person's risk for dementia.

But doctors who treat both conditions said the connection makes
sense. For one, dementia and atrial fibrillation share the same
risk factors.

A person with high blood pressure and diabetes is automatically
considered to be at a higher risk of both atrial fibrillation and
dementia, said Dr. Shadi Kalantarian, research fellow of the
Cardiac Arrhythmia Service at Massachusetts General Hospital.
Thacker's finding could have been called a coincidence if he
hadn't accounted for those risk factors, but he did, and the
connection between atrial fibrillation and dementia remained.

One cause for the lower test scores could be the fact that an
irregular heartbeat can lead to chronic blood flow problems,
possibly lowering the amount of oxygen and nutrients available to
the brain.

So-called
"silent" strokes could be another explanation. "People with
atrial fibrillation are more prone to forming blood clots in
their atrium," Kalantarian said. A large blood clot that lodges
in the brain will cause a noticeable stroke and, of course,
noticeable brain damage. However, a person could suffer a series
of mini 'silent' strokes and not even know it, Kalantarian said.

"The 'silent' means that you don't have the sudden signs of
stroke, but they are clearly not truly silent, because they cause
an insidious development of cognitive and gait impairment," said
Zazulia, who also thought silent strokes could be behind the
connection.

Incorporating brain imaging into future large, long-term studies
could show whether silent strokes are to blame for earlier signs
of dementia.

"If medical researchers could find the answer to that question of
why this happens, then we could have something useful for
patients," Thacker said.